Maybe it has been said before,
but what I notice is that when I make a selection
and show the histogram distribution I see the distribution of the whole image instead of the
distribution of the selected part. I think it would be much better if the histogram would
be calculated based on the selection, maybe this behavior should be selectable
in the settings file.

it would even make more sense that *ALL* the manipulations available for XnView would apply
to the selected area of an image, that would greatly enhance the possibilities of the program.
Maybe this wouldn't make sense for some of the manipulations,
but e.g. (auto) adjustment of brightness or mirroring are obvious I think.